1921] 



NATURAL SCIENCES OF PHILADELPHIA 



189 



2y.5- 



i\- 1 •.* ^ / / i/_\=i 



- > 



* ~.N- 



I -, 







' "' '-'-T'.^r- 





<^ rye 







I > 







r^^^-^' 



















Fig. 13. — Ideal vertical section of corundum in amphibolite at Hunters, Iredell 

 County, N. C. (Pratt and Lewis); (a) a feldspar vein more or less altered 

 to kaolin and often bearing corundum; (b) vermiculite zones carrying corun- 

 dum;, (c) radiating sheaths of actinolite enclosing some amphibolite; (d) 

 amphibolite often reduced to a mass of ocherous clay containing needles 

 of hornblende and scales of vermiculite. 



Table 5. Analyses of the Plagioclase Feldspars of 

 THE North Carolina Corundum Veins. 



A. Oligoclase, Corundum Hill mine, Macon County, N. C. H. M. Keller, 

 U. S. Geol. Surv. Bull., 74, p. 55. 



B. Andesine. Buck Creek mine, Clay County, N. C. Snow-white to bluish- 

 white masses, striated. G. A. Koenig, Proc. Am. Phil. Soc, 13: 375, 1873. 



C. Andesine. Buck Creek mine. Clay County, N. C. T. M. Chatard, Proc. 

 Am. Phil. Soc, 13: 375, 1873. 



D. Labradorite. Buck Creek mine, Clay County, N. C. White lustrous 

 cleavage masses. W. H. Jarden, Bull. U. S. Geol. Surv., 74, p. 54. 



B 



C 



D 



SiOj 63.32 



AUO3 35.19 



Fe.,03 



MgO 



CaO 5.01 



Na^O 8.02 



K2O 0.25 



Ignition .... 



101.79 

 Sp.gr 



